The present invention relates generally to drywall construction and is particularly concerned with a hopper apparatus and method for applying drywall mud or joint compound to corner beads or tape-on-trims prior to their attachment to joints or corners between adjacent drywall panels.
Corner beads are elongate, narrow strips of metal, plastic, or metal with a paper face on one side, or the like folded or angled along their longitudinal center line, or along a line offset from the center line in some cases, to produce a generally v-shaped cross-section. They are made in various angles and corner shapes, including sharp 90 degree angle corners, sharp corners at other angles, rounded or so-called “bullnose” corners of various angles, and offset or L-shaped corners. Corner beads are also designed for covering both inside (concave) and outside (convex) corners. For application to an inside corner, drywall mud is applied to the outside (convex) faces of an inside corner bead. For application to an outside corner, drywall mud is applied to the inside (concave) faces of an outside corner bead. Joint compound is applied to the appropriate faces of the bead, and the bead is then pressed against the corner, with the joint compound forming an adhesive joint between the bead and corner.
Although drywall mud or joint compound may be applied to corner beads by hand, this is a time consuming and inconvenient process. Hopper devices have been proposed in the past for applying joint compound to the inside faces of an outside corner bead. One such apparatus is described in U.S. Pat. No. 5,169,449 of Raught. The apparatus comprises a hopper with a V-shaped trough in its base, and triangular shaped end walls at opposite ends of the trough forming a generally V-shaped gap between the lower edge of each end wall and the trough. Removable end panels are adjustably secured to the end panels to adjust the height of the gap. A corner bead is fed through the base of the hopper from one end wall opening to the opposite end wall opening, and drywall mud in the hopper will be applied to the upwardly facing surfaces of the corner bead. All except a thin layer will be scraped off by the edge of the end panel as the corner bead exits the hopper. Removable liners may be placed into the hopper to define different trough cross-sectional shapes, corresponding to different shapes of corner bead, and associated with end panels with corresponding edge shapes.
The Convertible Hopper manufactured by Pla-Cor Incorporated, of Santee, Calif. has an open base across which a feeder is secured, the feeder having a V-shaped trough for receiving an outside corner bead. Removable panels or gates are secured to opposite end walls of the hopper for forming a V-shaped inlet and outlet opening with the opposing surface of the feeder at opposite ends of the feeder. The feeder can also be adjusted for different shapes of outside corner bead, by placing a feeder insert comprising a generally V-shaped trough over the main feeder. This requires removal of the feeder from the hopper, placement of the feeder insert over the feeder, and re-attachment of the feeder insert and feeder to the hopper. This hopper apparatus is designed to be converted between 90 degree corner beads, ¾ inch bullnose, and 1½ inch bullnose corner beads.
One problem with prior art hoppers having corner bead feeders for applying joint compound is that they can only be used for outside corner beads, i.e. corner beads that are applied over outside, or convex, corners in a building. However, a large number of the corner joints between adjacent drywall panels are inside corners. Up to now, there has been no effective and accurate means to apply drywall mud to inside corner beads.